Implementation of expression evaluator based on JDI

Allows user to evaluate any Scala expression in context of some breakpoint
during debug. Expression is transformed in multiple phases and evaluated
using calls to remote, debuged machine and result is fetched back to user.

Because of complexity of Scala language, implementation details of JVM
platform and necessity for manual evaluation not all Scala features are
supported yet.

Co-authored-by:
 - Pawel Batko <pawel.batko@gmail.com>
 - Piotr Kukielka <piotr.kukielka@gmail.com>
 - Jerzy Muller <sidus.gemini@gmail.com>
 - Michal Pociecha <michal.pociecha@gmail.com>
 - Krzysztof Romanowski <romanowski.kr@gmail.com>
Test suite for operations on primitives

Test includes:
 - `!`, `==`, `!=`, `<`, `>`, `<=`, `>=` on Booleans,
 - `||`, `&&`, `&`, `|`, `^` on Booleans,
 - `+`, `-`, `*`, `/`, `%` on numerics,
 - bitwise `&`, `|`, `<<`, `>>`, `>>>`, `^` on integrals,
 - unary `+`, `-` on numerics and unary `~` on integrals,
 - type conversion (`toXXX`)
 - and various other methods defined in `ScalaNumberProxy`,
   `RichXXX`, `Fractional` and `Integral`.
Implementation of conditional breakpoints

Based on expression evaluator.
User interface for expression evaluator

Complete with history command, tree view for values, simple content
proposal and multiple configuration parameters.
RunSelectionInInterpreter action added

Runs currently selected text in expression evaluator view.
AUTHORS file updated with names of expression evaluator authors